The present invention relates to socket-type setting tools for setting threaded collars in general, and, more in particular, to a driver having wrenching and deforming flats that tighten a collar onto a pin and against a sheet and thereafter crush lobes of the collar upon the application of a predetermined amount of force corresponding to a desired clamp-up load of the collar on the sheet.
The parent to this application is directed to a fastener system that employs an internally threaded collar (nut) and an externally threaded pin (bolt). In a very general way the collar and pin cooperate like a standard nut and bolt in that they are adapted to clamp between them sheets or workpieces. The collar, however, has plastically deformable lobes extending longitudinally along an outer surface. These lobes in turn have surfaces which parallel the axis of the collar. The lobes are capable of being deformed plastically and to deform material of the collar radially inward of the lobes plastically into void volumes between the collar and the pin. Preferably, these void volumes are defined by flutes on the pin. Collar material displaced into the flutes forms an interference lock between the collar and the pin. The lock occurs simultaneously with the attainment of a desired clamp-up load on the sheets or workpieces. With the plastic deformation of the lobes, they disappear as wrenching means and therefore the load on the sheets cannot exceed the design load.
The parent application describes a driver having a deltoid socket. The socket has flats which intermediate the apexes of the deltoid engage the lobes of the collar. These flats crush the lobes into the body of the collar. The minimum radius to each of the flats corresponds to the radius of the collar at the base of the lobes. Stated differently, this corresponds to the radius of the collar to a right cylindrical section of the collar from which the lobes protrude.
It is desirable that the driver have long life and that its working surfaces be of the same radius at corresponding points. The latter requirement is necessary so that the amount of material of the lobes failed in radial compression be predictable and the same from tool-to-tool to hold the clamp-up load to within close tolerances. It is also desirable that the driver not cant relative to the axis of the collar during the setting of the collar in order that the lobes be failed properly. For example, if there were some canting of the driver, not all of the material of the lobes would fail and the clamp-up load would fall short of that desired.